In the nearly four decades of various cycles of the Afghan war, few alliances are as baffling as Iran’s not-so-secret cooperation with the Afghan Taliban.

Tehran’s Shi’ite clerical regime was a key backer of the Northern Alliance -- the main battlefield enemy of the hard-line Sunni Taliban regime in the 1990s. The two almost went to war after Iranian diplomats were killed during the Taliban takeover of the northern city of Mazar-e Sharif in 1998.

In recent years, however, Iran and the Taliban have moved closer to one another, to the extent that after a U.S. drone killed former Taliban leader Mullah Akhtar Mohammad in southwestern Pakistan last May, it was revealed he was returning from a trip to Iran.

The burgeoning contacts and Tehran’s alleged covert support for the Afghan Taliban, most of which is reportedly focused on countering the ultraradical anti-Shi’ite Islamic State militants, is expected to attract attention from U.S. President Donald Trump’s administration. Amid rising tensions between Washington and Tehran, U.S. Defense Secretary James Mattis recently declared Iran the “world’s biggest sponsor of terrorism.”

RFE/RL Media Relations Manager Muhammad Tahir moderated our discussion from Washington. Ahmad Majidyar, a managing director of the Middle East Think Tank, and Eric Jones, editor-in-chief of the Foreign Intrigue website, joined us from Washington. As usual, I pitched in from Prague.